摘要
On the basis of the FLP (frustrated Lewis pair) principle, a new strategy has been proposed to construct the "frustration" in de- signing metal-free hydrogen activation compounds, by using FMO (frontier molecular orbital) analyses and quantum mechanics calculations. Unlike the known FLPs which use bulky substituents to prevent them from forming stable Lewis acid/base com- plexes, the new approach encumbers the intramolecular π donation from the electron donor to the acceptor (e.g. in BH2NH2) by using a CH2 bridge (giving BH2CH2NH2). The strategy is simple and effective. Its effectiveness is demonstrated by the small hy- drogen activation energy (12.0 kcal/mol) of the model molecule (BH2CH2NH2), which is significantly less than the 42.7 kcal/mol of BH2NH2 and also less than the 18.5 kcal/mol of BH2PH2 whose derivative, R2PB(C6F5)2, has been experimentally shown to be able to activate hydrogen. We also exemplified how to use the strategy to design experimentally more realizable molecules. The example shows promises as a hydrogen activation agent. The strategy can be used to design metal-free catalysts for direct hydro-genation.
On the basis of the FLP （frustrated Lewis pair） principle, a new strategy has been proposed to construct the ＂frustration＂ in designing metal-free hydrogen activation compounds, by using FMO （frontier molecular orbital） analyses and quantum mechanics calculations. Unlike the known FLPs which use bulky substituents to prevent them from forming stable Lewis acid/base complexes, the new approach encumbers the intramolecular n donation from the electron donor to the acceptor （e.g. in BH2NH2） by using a CH2 bridge （giving BH2CH2NH2）. The strategy is simple and effective. Its effectiveness is demonstrated by the small hy- drogen activation energy （12.0 kcal/mol） of the model molecule （BH2CH2NH2）, which is significantly less than the 42.7 kcal/mol of BH2NH2 and also less than the 18.5 kcal/mol of BH2PH2 whose derivative, R2PB（C6F5）2, has been experimentally shown to be able to activate hydrogen. We also exemplified how to use the strategy to design experimentally more realizable molecules. The example shows promises as a hydrogen activation agent. The strategy can be used to design metal-free catalysts for direct hydrogenation.
基金
supported by the Hundred Talents Program of the Chinese Academy of Sciences and Nationd Nataral Science Foundation of China (Grant No.20773160)
关键词
金属化合物
设计实验
氢化合物
分子内
活化能
量子力学计算
前线分子轨道
路易斯酸
metal-free hydrogen activation, metal-free hydrogenation catalysts, π donation encumbrance, frustrated Lewis pair, ab initio calculations
